Leveling system for a construction machine

ABSTRACT

Leveling system for a construction machine, in particular a road construction machine or a road finishing machine comprising: a layer thickness measurement system, configured to measure a current layer thickness and determine respective actual layer thickness values for a plurality of positions, a processor configured to determine, based on a layer thickness profile including a plurality of set layer thickness values allocated to a plurality of the positions, as well as the actual layer thickness values for the positions, control values per position for height regulation of a tool of the construction machine.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from German Patent Application No. 102022201294.1, which was filed on Feb. 08, 2022, and is incorporated herein in its entirety by reference.

Embodiments of the present invention relate to a leveling system for a construction machine, in particular, a road construction machine, such as a road finishing machine or a road milling machine. Embodiments relate to a leveling system with a layer thickness measurement system.

Further embodiments relate to a construction machine (road construction machine, such as road finishing machine or road milling machine) having a respective leveling system. A further embodiment relates to an apparatus for determining a layer thickness profile. Further embodiments relate to the respective methods for leveling and for determining a layer thickness profile and respective computer programs.

BACKGROUND OF THE INVENTION

Leveling systems are used, for example, in road construction machines, such as road finishing machines or road milling machines. By using leveling systems, for example in road finishing machines, the height of the placement tool (the placement screed) as well as the inclination (cross-slope) is controlled, such that the placed layer is placed with the respective layer thickness and inclination. By the leveling system, unevenness in the underground is leveled out accordingly. Here, during the placement process, a respective actual height of the road finishing machine or the placement tool (screed) with respect to the underground or with respect to the already applied layer is scanned in order to be able to control the placement tool accordingly in dependence on the underground variations. Consequently, in leveling systems, a sensor holder running in parallel to the direction of travel is used, which extends, for example, across a length of 12 m. Such a sensor holder is illustrated in FIG. 1 a . FIG. 1 a shows a road finishing machine 10 having a sensor holder 12 and four sensors 14 a-14 d. Here, the sensor 14 b is arranged behind the screed 10 b. By the illustrated sensor holder having the four sensors 14 a-14 d, waves in the range of 4 to 8 m can be well scanned and then leveled out.

For correspondingly longer waves, additional height regulation can be performed by means of a total station as illustrated in FIG. 1 b . FIG. 1 b shows a road finishing machine 10 having a screed 10 b. The height adjustment of the screed is controlled at the tow point 10 z via the tow point cylinder 10 zz as explained already in the context of FIG. 1 a . Additionally or alternatively, the height of the screed 10 b can also be controlled by using the components 14 la 1 and 14 la 2 as well as 14 t. The total station 14 t introduces an external reference that emits a laser beam at a predetermined height. This laser beam emitted, for example in parallel to the underground or a reference is then directly received by the height sensor 14 la 1 or indirectly after reflection by the 360° prism 14 la 2. Thereby, the actual height of the screed with respect to a stationary reference height can be determined. Due to the stationary reference height, the actual height is not subject to long-wave variations that cannot be detected by means of the sensor arrangement of FIG. 1 . Further, by using the total station as a virtual reference, it is possible to dispense with other references, such as cords, etc. The disadvantage of the usage of the total station is that the same has to be expensively calibrated and frequently one total station is not enough, especially for longer screeds. Therefore, there is the need for an improved approach.

SUMMARY

According to an embodiment, a levelling system for a construction machine, in particular a road construction machine or a road finishing machine or a road milling machine, may have: a layer thickness measurement system configured to measure a layer thickness currently to be applied or to be removed and respective actual layer thickness values for a plurality of positions or respective predicted actual layer thickness values for a plurality of positions, a processor configured to determine, based on a layer thickness profile including a plurality of set layer thickness values allocated to the plurality of the positions, as well as the actual layer thickness values or predicted actual layer thickness values for the positions, control values per position for height regulation of a tool of the construction machine.

Another embodiment may have a construction machine, in particular road construction machine or road finishing machine or road milling machine having an inventive leveling system.

According to another embodiment, an apparatus for determining a layer thickness profile including a plurality of layer thickness values allocated to a plurality of positions may have: an interface for receiving an underground profile including a plurality of height values allocated to a plurality of the positions; an interface for receiving at least one set height or set depth; and a calculating unit for determining the layer thickness profile based on a difference between the plurality of height values allocated to a plurality of the positions and the at least one set height or set depth or a reference defined by the at least one set height or set depth.

According to another embodiment, a method for leveling for a construction machine, in particular a road construction machine or a road finishing machine or a road milling machine, may have the steps of: measuring a current layer thickness to be applied or to be removed and determining respective actual layer thickness values or predicted actual layer thickness values for a plurality of positions, determining control values per position for height regulation of a tool of the construction machine based on a layer thickness profile including a plurality of set layer thickness values allocated to a plurality of the positions as well as the actual layer thickness values or predicted actual layer thickness values for the positions.

According to another embodiment, a method for determining a layer thickness profile including a plurality of set layer thickness values allocated to a plurality of positions, may have the steps of: receiving an underground profile including a plurality of height values allocated to a plurality of the positions; receiving at least one set height or set depth; and determining the layer thickness profile based on a difference between the plurality of height values allocated to a plurality of the positions and the at least one set height or set depth or a reference defined by the at least one set height or set depth.

Another embodiment may have a non-transitory digital storage medium having a computer program stored thereon to perform any of the inventive methods when said computer program is run by a computer.

Embodiments of the present invention provide a leveling system for a construction machine, in particular a road construction machine or a road finishing machine or a road milling machine. The leveling system includes a layer thickness measurement system as well as a processor. The layer thickness measurement system is configured to measure a layer thickness currently to be applied or to be removed and to determine respective (predicted) actual layer thickness values for a plurality of positions (e.g., along a direction of travel of the construction machine). Here, for example, several current layer thickness values are obtained for a plurality of (successive) positions. In other words, this plurality of layer thickness values can be referred to as actual layer thickness profile. The processor is configured to determine, based on a layer thickness profile (set layer thickness profile) including a plurality of set layer thickness values allocated to the plurality of positions, as well as the (predicted) actual layer thickness values for the respective positions, control values per (further) position for height regulation of a tool of the construction machine, e.g., the screed or the milling drum.

It should be noted that depending on the measurement system, the actual layer thickness value could be predicted starting from the currently measured layer thickness, as the individual sensors scan the underground in front of the screed without any applied layer. The prognosis is made based on the measured height values per position. Without regulation, the predicted actual layer thickness would be generated at the respective positions. The same is, for example, negative during layer removal (road milling machine) or positive during layer application (road finishing machine). A variation can take place where respective regulation based on the above-stated set layer thickness values.

According to the embodiments, the control values are determined per position for height regulation of the tool such that the tool is controlled according to the set layer thickness profile. According to embodiments, additionally, the tool is controlled by the control values such that a deviation between the actual layer thickness value profile and the set layer thickness value profile or the actual layer thickness value and the set layer thickness value is regulated per respective position.

According to embodiments, the control values per position are selected such that in the settled state of a tool, the actual layer thickness value per position essentially corresponds to the set layer thickness value. “Essentially” means, for example, ±20%, ±10%, ±5%, ±3% or ±1%, i.e., a deviation of a maximum of ±1%, ±3%, ±5%, ±10% or ±20% (depending on the variation) is allowable. For this, according to embodiments, the control values are derived such that height regulation of the tool is performed by considering the regulation path (offset between position of the regulation and completed regulation, e.g., offset between pivot point or virtual pivot point or screed back edge and tow point) of the tool along a direction of travel of the construction machine. According to embodiments, some type of correction value is determined per position based on a deviation between the set layer thickness value and the actual layer thickness value. This correction value is used, wherein, due to the explained offset, the same is not applied to the current position (the actual layer thickness value) but to a “future” or further position. In that way, for the “future” position, the height of the tool is determined based on the correction value and the set layer thickness value for the respective further position. For example, the control values per “further” position are selected such that the tool is raised and/or lowered according to the set layer thickness profile when reaching the “further” position in order to be moved to the set layer thickness value, per position, at a corresponding position. Additionally, the control values per further position can be selected such that a current deviation between an actual layer thickness value and a set layer thickness value is compensated or considered.

Thus, embodiments of the present invention are based on the finding that instead or in addition to the regulation at a fixed height value, regulation to varying set height values is performed according to a layer thickness profile in order to compensate for long wave unevenness. Here, starting from the unevenness scanned in advance, for example, a set layer thickness profile is scanned, which, when applied on the unevenness, forms an even surface together with the unevenness. For example, at positions of an unevenness hill, a thinner set layer thickness is provided than at locations of the unevenness valley. This applies, in particular, for road finishing machines or other construction machines applying a surface. In the case of a road milling machine or more generally the machine removing a surface, the set layer thickness profile corresponds to the profile that is to be removed from the surface. Here, at an unevenness hill, more material is removed than at an unevenness valley.

In both cases, as a result, a surface is provided that is even, in particular with respect to long-wave unevenness. By the continuous (set/actual) adjustment, drifting is prevented. Above that, the effort on site is also reduced, since measures such as total stations, etc., can be omitted.

According to embodiments, this means that the above-explained processor is configured to derive the control values from the layer thickness profile, such that a layer to be smoothed by the tool or to be applied by the tool forms an even surface along a direction of travel of the construction machine on an (uneven or wave-like) underground profile. This is advantageously performed as discussed above, even for long-wave unevenness. Here, it should be noted that the layer to be applied (to be placed) or the layer to be smoothed can also have a second dimension transversal to the direction of travel, apart from the first dimension along the direction of travel. The control values are derived from the layer thickness profile such that a layer to be applied (to be placed) or to be smoothed by the tool on the underground profile forms an even surface along a spanned plane. The plane extends along the first and the second dimension. According to embodiments, this is performed, for example, in that the tool can be controlled in height both on the first side and on the second side on the construction machine (left-right). The tool, such as the screed, extends from the first side to the second side of the construction machine or beyond the first and second side of the construction machine and provides an even surface. Depending on the height of the two actuators for the tool or depending on the relative height of the two actuators for the tool, inclination adjustment is performed. The control values for the two actuators are determined in dependence on the set inclination as well as in dependence on the two-dimensional underground profile according to further embodiments. This means that, according to embodiments, the layer thickness measurement system forms, together with a processor, a first control circuit for a first side (left or right of the tool). The layer thickness measurement system (or a further layer thickness measurement system) forms, together with the processor, a second control circuit for a second (different) side of the tool. According to further embodiments, the two control circuits interact in order to control the tool accordingly for intermediate positions between the first and the second side of the tool, such that the actual layer thickness essentially corresponds to the set layer thickness for intermediate positions in the settled state.

According to a simple variation, the layer thickness measurement system can be formed by two height sensors, wherein the first height sensor is arranged, for example, behind the screed and also measures the deposited or leveled layer and determines a respective height value, while the second height sensor is applied in front of the screed and determines a height value with respect to the underground or the layer that is not yet leveled. If a simple case of comparable application heights is assumed, for example, the layer thickness can be determined by differentiation. In the case of a non-identical application height, either offsets can be used, which leads to very exact results when the distances along the direction of travel between sensor and pivot point are the same. Regarding the pivot point, it should be noted that the same could be formed, for example, by the screed back edge. By considering the theorem of intersecting lines, obviously, arrangements with different distances are possible. According to embodiments, the two height sensors are firmly connected to the screed, wherein “firmly” is to be interpreted in that a predetermined geometrical relationship between screed and sensors is given. By the suspension, the two sensors move together with the screed, i.e., the same rotate together and experience the same lifting movement (like the screed).

According to embodiments, the sensor arrangement comprises at least two, even at least three or even at least four sensors that are arranged at a carrier extending along the direction of travel of the construction machine. According to further embodiments, the layer thickness measurement system can be integrated in this sensor arrangement.

According to embodiments, the layer thickness profile is determined in dependence on an underground profile. The underground profile also has a first dimension along the direction of travel and can have a second dimension transversal to the direction of travel. According to embodiments, this underground profile is scanned in advance, such that also (in advance or in real time) a respective determination of the layer thickness profile can take place with the set layer thickness value per position. Thereby, the layer thickness profile can have varying set layer thickness values across the positions and/or along the direction of travel.

As already mentioned above, each set layer thickness value is allocated to a position for which an actual layer thickness value can be determined. The determination of the respective position takes place, for example, with a position sensor or GNSS sensor. According to embodiments, the same can be coupled to the tool/the screed or alternatively also to the construction machine. The position sensor or GNSS sensor is configured to determine the positions for the actual layer thickness values, in particular positions along the direction of travel.

In the following, further aspects regarding the regulation will be explained. It should be noted that according to embodiments, a minimum layer thickness could be provided in the layer thickness profile. This minimum layer thickness defines the set layer thickness value at a wave hill of the underground profile. The control values are derived according to the predetermined minimum layer thickness per position.

Thus, advantageously, the above-discussed approach allows leveling of a layer thickness, e.g., a layer to be applied or a layer to be removed that regulates particularly long-wave unevenness. In the basic variation, this leveling involves a non-conventional leveling technology of a conventional leveling system. According to a further embodiment, the explained leveling system can be combined with a conventional leveling system or can be integrated in a conventional leveling system. In other words, this means that the above-discussed leveling system can comprise functionalities of a conventional leveling system. According to embodiments, this also means that the processor of the above-discussed leveling system comprises an evenness regulator configured to determine the control values by using sensor values, such that an even surface is generated. As already discussed in the context of the conventional technology, the evenness regulator can comprise, for example, several distance sensors that are arranged transversal to the direction of travel of the construction machine and measure a distance to the underground. It is advantageous that the layer thickness measurement system that is, for example, to be used, uses comparable or the same distance sensors. According to embodiments, the layer thickness measurement system can be based on two distance sensors that are arranged around the pivot point of the screed, i.e., one in front of the screed and one behind the screed and determine, for example, the layer thickness by the difference of the two height values. Further implementations having other constellations will be discussed below. According to further embodiments, the processor can comprise a regulation path comprising, for example, a P component and/or an IT component and/or a PT component. Additionally or alternatively, the regulation path can also be regulated by means of a prediction model. This prediction model is particularly advantageous for the above-discussed leveling approach based on the layer thickness values, as a temporal offset or in particular a spatial offset of several centimeters or even meters is present between regulation time and actually performed change of the applied layer thickness profile is. This offset depends on parameters such as screed inclination angle, speed of the construction machine, asphalt temperature, asphalt thickness, etc. These dependencies can also be considered by using the prediction model.

A further embodiment relates to a construction machine, a road construction machine or a road finishing machine with respective leveling system. According to further embodiments, a road milling machine or construction machine with milling function and a respective levelling system can be provided.

Further embodiments relate to an apparatus as well as a calculating unit for determining the layer thickness profile (including the plurality of layer thickness values allocated to the plurality of positions). The apparatus includes an interface as well as a calculating unit. The interface is configured for receiving an underground profile (e.g., a scanned underground profile) including a plurality of height values allocated to a plurality of the positions. Further, the at least one set height or set depth is received by this interface or a further interface. For example, the set height can be defined by a set height value or several set height values allocated to several positions. In conventional leveling systems or layer thickness measurement systems, a minimum layer thickness has been determined. The same corresponds, for example, to the set height. The calculating unit is configured for determining the layer thickness profile based on a difference between the plurality of height values allocated to a plurality of the positions and the at least one set height or set depth or a reference by the at least one set height or set depth. According to further embodiments, the apparatus includes an output interface for providing or exporting the layer thickness profile to a construction machine. Here, it should be noted again that the set height, according to further embodiments, can also be defined by several set height values allocated to a plurality of the positions or the at least one set depth can be defined by several set depth values allocated to a plurality of the positions. This is particularly relevant when different set heights result for left and right or along the direction of travel for setting an inclination. According to embodiments, the several set height values or the one set height value define a plane or 3D planes of a layer to be smoothed or to be produced (to be placed).

According to further embodiments, a method for leveling for a construction machine is provided. The method includes the steps of:

-   Measuring a current layer thickness to be applied or to be removed     and determining respective (predicted) actual layer thickness values     for a plurality of positions, -   Determining control values per position for height regulation of a     tool of the construction machine based on a layer thickness profile,     including a plurality of set layer thickness values allocated to a     plurality of the positions, as well as the (predicted) actual layer     thickness values for the positions.

A further embodiment relates to a method for determining the layer thickness profile, comprising:

-   Receiving an underground profile including a plurality of height     values allocated to a plurality of the positions; -   Receiving at least a set height or set depth; and -   Determining the layer thickness profile based on a difference     between the plurality of height values allocated to a plurality of     the positions and the at least one set height or set depth or a     reference defined by the at least one set height or set depth.

According to further embodiments, the method can be computer-implemented.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequently referring to the appended drawings, in which:

FIG. 1 a is a schematic illustration of a construction machine having a measurement system for a leveling system;

FIG. 1 b is a schematic illustration of a construction machine having a leveling system;

FIG. 2 a is a schematic block diagram of a leveling system according to a basic embodiment;

FIG. 2 b is a schematic illustration of a layer thickness measurement system according to embodiments;

FIGS. 2 c and 2 d are schematic illustrations of a leveling system by using a layer thickness measurement system according to extended embodiments;

FIG. 2 e is a schematic illustration of a layer thickness measurement system according to embodiments;

FIGS. 3 a and 3 b are schematic illustrations of underground profiles and layer thickness profiles for explaining embodiments;

FIG. 4 is a schematic illustration of an underground profile in combination with a set layer thickness profile with allocated parameters for discussing embodiments;

FIGS. 5 a and 5 b are schematic block diagrams of leveling systems according to extended embodiments;

FIGS. 6 a and 6 b are schematic illustrations for explaining the regulation behavior of a screed as tool of a construction machine;

FIGS. 7 a and 7 b is a schematic illustration of a leveling system during usage for a milling machine according to embodiments;

FIGS. 8 a and 8 b are schematic illustrations together with measurement values for explaining the compensation of long waves according to embodiments; and

FIG. 9 is a schematic block diagram for explaining the calibration process in a leveling system according to embodiments.

DETAILED DESCRIPTION OF THE INVENTION

Before embodiments of the present invention will be discussed below based on the accompanying drawings, it should be noted that equal elements and structures are provided with the same reference numbers, such that the description of the same is inter-applicable or inter-exchangeable.

Embodiments of the present invention provide a leveling system. The leveling system can advantageously be used in a construction machine, in particular a road finishing machine 10 as shown in FIGS. 1 a and 1 b .

The leveling system 100 is schematically shown in FIG. 2 a . The leveling system 100 includes a layer thickness measurement system 110 as well as a processor 130. The layer thickness measurement system 110 is here again sketched exemplarily. The same includes, for example, a carrier 12 that is arranged at the screed 10 b of the construction machine and carries two distance measurement devices 14 a and 14 b, e.g., ultrasound sensors. The first ultrasound sensor 14 a is arranged in front of the screed in the direction of travel, while the second ultrasound sensor 14 b is arranged behind the screed scene in the direction of travel. Each of these sensors 14 a and 14 b determines the distance A or B with respect to the underground or with respect to the deposited layer. By forming the difference of the two distances A and B, the layer thickness can be determined. Details for this will be discussed below. The determined layer thickness values S1, S2, ... for the positions P1, P2 along the direction of travel are transmitted to the processor 130. Above that, the processor 130 receives a (set) layer thickness profile 120. The layer thickness profile 120 includes set layer thickness values S_(set1), S_(set2), ... for the respective positions. As illustrated in block 120 or also in FIG. 3 a , the layer thickness profile 120 includes differential heights applied across the individual positions forming an even layer together with the underground 122. As illustrated in FIG. 3 b , the underground 122 comprises waves, here long waves in the range of 15 to 100 m. The wave valleys are marked by 122 t, the wave hills by 122 b. A greater layer thickness is provided in the region of the wave valleys 122 t, while a smaller layer thickness is provided in the range of the wave hills 122 b.

The processor 130 determines the control values C1, C2 allocated to the individual positions such that the tool, here the screed 10 b, is controlled into the respective height in order to move to the respective set values S_(set1), S_(set2), the positions. The control values C1, C2 act on the tow point adjustment and, as a result, raise or lower the screed. The control values, for example, can be specific distance indications by how much the tow point is to be shifted. In this case, both positive as well as negative control values would be possible since the tow point can be both raised as well as lowered. For example, such a control value can be directly proportional to the determined difference between the set layer thicknesses and actual layer thicknesses. According to embodiments, a translation ratio is to be considered, as a tow point shift results in x longitudinal units (screed shift x, e.g., between 0.1 and 10 or 0.01 and 100) depending on the geometry of the screed suspension. Depending on the geometry, an indirect proportionality can be provided. According to a further variation, it would also be possible that the control values only indicate that a tow point rise or a tow point lowering is needed. This is, for example, a binary regulation or a regulation with three states (-1 lowering, +1 raising and 0 no change of the tow point). This type of control value can also be combined with the above discussed control values, such that, for example, for lowering and raising, two or three (generally more) possible control values indicating the degree of the change are possible. As already seen based on FIG. 1 b , the height of the tow point 10 z is adjusted via the tow point cylinder 10 zz, which has, however, only an indirect influence on the height of the screed 10 b or in particular the screed back edge 10 bk.

Starting from the control 130 by considering the layer thickness profile 120, theoretically, a perfect surface is formed. Since in practice the height of the tool and hence the applied layer thickness depends on further parameters apart from the adjusted height at the tow point cylinder 10 zz (current tow point adjustment), according to embodiments, the actual layer thickness S1, S2 per positon is also considered. Here, it should be noted that the values referred to as actual layer thickness values are measured, for example, with respect to the underground before the layer is applied, such that the same are predicted actual layer thickness values or also generally height values. In that way, the term actual layer thickness value is to be considered synonymous to the term actual height value. As can be seen from the arrangement of the measurement system of FIG. 1 a in front of the screed (cf. sensor arrangement 14 a, 14 c and 14 d) scanning takes place with respect to the underground in front of the screed, i.e., the position allocated to a fixed length offset starting from the screed in the direction of travel or starting from the screed back edge in the direction of travel.

Here, it should be noted that, according to embodiments, for example at a position P1, the set value S_(set1) is maintained and the layer thickness height S1 at the position P1 can be compared, wherein then the control signal C_(1+offset) is output. The background is that at the time when the height S1 can be determined, tow point adjustment for a further position already takes place, which is offset by a regulation path. In that way, the derived control signal C_(1+offset) is to be considered as some sort of compensation signal, wherein then for the further (offset) position P_(1+offset) (for example P3), the respective set height S_(set3) is also considered together with the compensation signal C_(1+offset).

This results in the constellation that the control signal for the further position depends on the set-actual comparison of the first position P1, wherein the set height for the further position, e.g., S_(set3), is also considered. Here, it should be noted that the further position, here P3, is offset by an offset from the first position P1, which can be constant, at least during operation, and which is considered to be constant. As already discussed above, this offset depends on the different parameters such as velocity of the construction vehicle, asphalt temperature, asphalt mixture, inclination angle of the screed, etc.

The principle can be applied, e.g., to road finishing machines with a layer height to be applied but also to road milling machines with a layer depth to be removed. In the road finishing machine, a set layer thickness/set height is determined per positon, in the road milling machine a set layer depth/set depth.

This offset becomes more obvious based on the positions of the layer thickness regulating tool 10 b, the tow point adjustment 10 zz, as shown in the top view of FIG. 2 b .

FIG. 2 b shows a construction machine 10 with a screed 10 b, a layer thickness measurement system 14 r comprising a first sensor 14 a and a second sensor 14 b in this embodiment. The same are mounted to the screed 10 b by means of a carrier 12, such that the first sensor 14 a measures in front of the screed and the second sensor 14 b behind the screed. The first sensor 14 a measures with respect to the underground while the second sensor 14 b measures with respect to the applied layer.

Above that, according to embodiments, a further layer thickness measurement system 14 l can be provided, which is structured analogously to the layer thickness measurement system 14 r. The layer thickness measurement system 14 r is located, for example, on the right side of the screed 10 b, while the layer thickness measurement system 14 l is arranged on the left side of the screed 10 l. As already discussed above, the layer thickness measurement system 14 l and 14 r measures a height with respect to the underground. Assuming that both sensors 14 a and 14 b are arranged in the same application height, a layer thickness can be determined starting from the difference of the two height values. When tilting the screed, the distances also change indirectly proportionally. With the same lever arm lengths, i.e., the horizontal distance of the sensors 14 a and 14 b with respect to the pivot point, the layer thickness can still be determined based on the difference. According to embodiments, in the case of lever arms of different lengths, the theory of intersecting lines can be considered. Different measurement methods for the layer thickness determination by means of distance sensors are explained, for example, in EP 2921588 or EP 3048199 or EP 3228981. Above that, according to further embodiments, other methods for layer thickness measurement can be considered. However, it is of particular advantage of the above discussed layer thickness measurement that distance sensors can be used that are also used in conventional leveling systems.

Here, it should be noted that the layer thickness is typically determined in the region of the screed. The position is marked by reference number 140. According to further embodiments, a position sensor, such as a GNSS sensor, can be provided at the position 140, to allocate a position to the layer thickness, which improves the comparison of the set layer thickness to the actual layer thickness per position. Above that, a further position sensor 142 can be provided which is provided, for example, in the area of the tow point. As already explained above, the shift takes place at the tow point for positions, which are then approached later by the screed considering the offset. The usage of two position sensors advantageously allows the allocation of the positions to the offset between the current (screed) position and the further position (position of the tow point shift). According to embodiments, obviously, only one sensor can be provided and the offset can be calculated based on the driving speed or the same. Apart from the layer thickness measurement system 14, according to embodiments, a further sensor arrangement, here the sensor arrangement 24, can be provided. The sensor arrangement 24 also comprises distance sensors that measure the distance to the underground. These sensor arrangements 24 are directly connected to the chassis of the road construction machine 10 and scan the unevenness. This sensor arrangement can either be provided on the one side of the construction machine or on both sides of the construction machine.

Starting from the arrangement of FIG. 2 c , the leveling system will be explained. The constellation of FIG. 2 c shows the construction machine 10 with the screed 10 b as well as two layer thickness measurement system 14 l and 14 r for the two different sides of the screed 10 b. Each side is considered separately, for example, and receives set values S_(set) via a database 150. The database 150 can, for example, be installed on the notebook 152 or can be retrieved via the same. The notebook 152 or generally part of the leveling system with communication means or an interface provides the set data S_(set) to the two control circuits 130 l and 130 r. The same control the tow point currently on the left and right (not illustrated) according to the set values S_(set) for the future screed positions and the obtained deviations of a current screed position.

FIG. 2 d shows a further variation. Here it is indicated that one of the two control circuits 130 l or 130 r acts as master while the other one operates as slave. As can be seen, the control circuit 130 l receives the distance values from the measurement apparatus 14 l, while the control circuit 130 r receives the distance values from the measurement apparatus 14 r. In this embodiment, the arrangement 14 l, i.e., the measurement arrangement 14 r comprises three distance sensors 14 a, 14 b and 14 c each. 14 a is located between 14 b and 14 c and measures, for example, the height in the area in front of the screed or in the area of the tow point 10 z, while 14 c measures further forward towards the underground in the direction of travel. The layer thickness measurement system 14 l, 14 r can either use the two sensors 14 a and 14 b by forming the difference or also the sensor 14 c, 14 b or alternatively also all three sensors. Here, for example, the distance value is measured, averaged by means of the sensors 14 a and 14 c and the difference is taken together with the distance value of the distance sensor 14 b.

The whole sensor arrangement 14 can also be extended, for example by the usage of more than three sensors. This is illustrated, for example, in FIG. 2 e .

FIG. 2 e shows a construction machine 10 with a respective control circuit 130 as well as a sensor arrangement 14. The same includes four sensors 14 a, 14 b, 14 c and 14 d that are mounted to a common carrier 12. The sensors illustrated herein can be configured as so-called superski sensors, each comprising a plurality of sensor heads.

The sensors 14 a and 14 b together form a layer thickness measurement system 14. The sensors 14 a, 14 b can also be used for measurement value determination for functions of a conventional leveling system (for short wave). Here, advantageously, additional sensors can be used, for example, in the direction of travel in front of the sensors 14 a and 14 b. This means that the sensor arrangement 14 (14 l, 14 r) in the version with two sensors 14 a and 14 b each or in the version with more than two sensors 14 a to 14 d can be used both for the conventional leveling system as well as for the described leveling system for long waves. Obviously, a layer thickness can be determined directly by the sensors (14 a, 14 b).

According to embodiments, the system is configured as described above in order to compensate long-wave unevenness. According to further embodiments, additionally, short and unevenness can be compensated, e.g., based on conventional leveling technologies.

FIG. 4 shows a layer thickness profile 120′ for producing an even surface 125 of the layer to be applied. The underground profile 122 which is, e.g., scanned in advance, includes elevations and depressions. For example, scanning is performed at a distance of 3 m, wherein, apart from the height with respect to a reference, inclination angles etc., can be included. Starting from the deviation to the reference (cf. Δh_(set)), a layer thickness profile (cf. “thickness left” or “thickness right”) is derived separately for the two control circuits. A deviation from the reference for two points can also be considered (Δh_(two)).

With reference to FIG. 5 , the control circuit 103 is extended by an evenness regulator. With the layer thickness control circuit 130, the actual layer thickness S1, ... is determined based on the actual height values and compared to the set layer thickness (see comparator 131). This regulation can be performed as above by considering a prediction model 137. Above that, according to embodiments, an evenness regulator 142 can be provided. The same regulates the evenness in the area of the tow point with a P component or PT component, in dependence on a height sensor, e.g., the height sensor 14 a.

In the area of the screed, the evenness by using a P or PT component. This evenness regulation takes place without considering the prediction model 137.

With reference to FIG. 5 b , the model will be explained again in detail. FIG. 5 b shows the screed 10 b that is pulled across the tow point 10 z. The evenness is again adapted by means of the evenness regulator 142. This evenness regulator 142 regulates the tow point cylinder behaving like an IT1 component. As a feedback loop, the height sensor value is determined in the area of the tow point and fed back to the evenness regulator 142 after optional filtering (cf. filter 144). This is a secondary control circuit of the evenness control circuit. As already mentioned, the evenness control circuit comprises the P component and the IT1 component. Starting therefrom, the screed showing PT2 behavior is regulated. This results in a height at the screed back edge, which can be determined by means of the sensor 14 b or generally the sensor arrangement 14. After optional filtering by means of the filter 146, the actual height value is compared to the set height value, such that tow point adjustment can take place in a further control circuit by using the prediction model 137. By the sensor arrangement 14 in connection with the filter 146, a superimposed control circuit is provided, which corresponds to the control circuit 130 as explained above.

As already explained above, adjusting the tow point does not result in an immediate change of the layer thickness height. The background is a so-called settling process. The same is illustrated in FIG. 6 a . At a point P1, the tow point is adjusted accordingly to reach other screed heights as illustrated based on curve 60. Here, the tow point adjustment also takes place with a certain transient. The screed follows the tow point shift with a certain lag, which is why a so-called “overshoot” or “undershoot” can occur, i.e., that the screed dips into the other direction shortly after the point P1, which is illustrated based on the curve 62. The height adjustment of the screed 10 b is terminated, at the latest at point P2, which is approximately one tow arm length apart from point P1.

Above that, this settling process can also be considered with respect to time. Adjusting the tow point 10 z takes, for example, half a second, here 0.4 s. Starting therefrom, the layer thickness changes in the area of the screed with a time factor of 0.5 s. When the system mainly implies that a rotation around the screed back edge 10 bk takes place, it should be noted that the pivot point is shifted slightly in the direction of the tow point as shown in the bottom half of the schematic illustration. The bottom half represents the cinematics of the overall system, wherein the position of the pivot point can also vary depending on the current conditions. Even when the conventional leveling control circuit is activated, changes occur over the path traveled (time), e.g., in the range between 1 and 20 min.

The above principle has been explained in particular in the context of road finishing machines (layer thickness to be applied), wherein the above principle obviously can also be applied to further machines, e.g., road construction machines that cause planarization. For example, a road milling machine can be regulated in height by the system. FIG. 7 a shows the regulation of a road milling machine with a milling drum 10 f and two height sensors 14 l and 14 r. The same measure a specific height depending on their offset with respect to the underground 11. When the drum 10 ftakes material from the underground 11, the measured height reduces as shown based on FIG. 7 b . This height gives indications on the removed layer and can hence be referred to as layer thickness system. Since the underground profile can also be determined in advance for road milling machines, by means of the same above-discussed principle, a layer thickness to be removed in the sense of a layer to be removed can be determined in advance, which can then be kept constant by using the illustrated measurement system in order to remove in particular long waves.

FIGS. 8 a and 8 b illustrate layer thickness values across the individual positions 1 to 15. Here, for example, the position distances are equidistant. An average desired height, here 5.0, is assumed. In a position, here position 1, the desired average layer thickness is determined as reference layer thickness and is applied essentially in parallel to the underground. The individual layer thickness values are determined such that a minimum layer thickness h_(min) and a maximum layer thickness h_(max) are each not undercut or exceeded. Because layer thickness values are also determined such that a layer thickness change is possible without changing the underground (cf. position 8 and 9) the cross-slope can be adjusted.

Here, it should be noted that a differentiation is made between the control units or man-machine interfaces MM2 (hand control unit) and the global control SSI (control computer).

FIG. 9 shows a calibration process. In a start procedure, the height is set to the correct height level and the same is determined as reference level. Further, the time set points are introduced into the system, such that the respective layer thickness profile for compensating long-wave screed unevenness and/or the desired cross-slope is known to the leveling system.

A further embodiment relates to a method for determining the set layer thickness profile. Here, for example, as discussed, the underground profile is scanned to determine, starting therefrom, the set layer thickness profile. Here, minimum and maximum can also be considered.

Here, it should be noted that the procedure of determining and using the set layer thickness profile is in particular used in the substructure layers. Due to the low thickness of the binder layer and cover layer, usually, longwave unevenness cannot be compensated in these layers.

Although some aspects have been described in the context of an apparatus, it is obvious that these aspects also represent a description of the corresponding method, such that a block or device of an apparatus also corresponds to a respective method step or a feature of a method step. Analogously, aspects described in the context of a method step also represent a description of a corresponding block or detail or feature of a corresponding apparatus. Some or all of the method steps may be performed by a hardware apparatus (or using a hardware apparatus), such as a microprocessor, a programmable computer or an electronic circuit. In some embodiments, some or several of the most important method steps may be performed by such an apparatus.

An inventively encoded signal, such as an audio signal or video signal or transport current signal, can be stored on a digital memory medium or can be transmitted on a transmission medium, such as a wireless transmission medium or a wired transmission medium, e.g., the internet.

The inventively encoded audio signal can be stored on a digital memory medium or can be transmitted on a transmission medium, such as a wireless transmission medium or a wired transmission medium, such as the internet.

Depending on certain implementation requirements, embodiments of the invention can be implemented in hardware or in software. The implementation can be performed using a digital storage medium, for example a floppy disk, a DVD, a Blu-Ray disc, a CD, an ROM, a PROM, an EPROM, an EEPROM or a FLASH memory, a hard drive or another magnetic or optical memory having electronically readable control signals stored thereon, which cooperate or are capable of cooperating with a programmable computer system such that the respective method is performed. Therefore, the digital storage medium may be computer readable.

Some embodiments according to the invention include a data carrier comprising electronically readable control signals, which are capable of cooperating with a programmable computer system, such that one of the methods described herein is performed.

Generally, embodiments of the present invention can be implemented as a computer program product with a program code, the program code being operative for performing one of the methods when the computer program product runs on a computer.

The program code may, for example, be stored on a machine readable carrier.

Other embodiments comprise the computer program for performing one of the methods described herein, wherein the computer program is stored on a machine readable carrier.

In other words, an embodiment of the inventive method is, therefore, a computer program comprising a program code for performing one of the methods described herein, when the computer program runs on a computer.

A further embodiment of the inventive method is, therefore, a data carrier (or a digital storage medium or a computer-readable medium) comprising, recorded thereon, the computer program for performing one of the methods described herein. The data carrier, the digital storage medium, or the computer-readable medium are typically tangible or nonvolatile.

A further embodiment of the inventive method is, therefore, a data stream or a sequence of signals representing the computer program for performing one of the methods described herein. The data stream or the sequence of signals may, for example, be configured to be transferred via a data communication connection, for example via the Internet.

A further embodiment comprises a processing means, for example a computer, or a programmable logic device, configured to or adapted to perform one of the methods described herein.

A further embodiment comprises a computer having installed thereon the computer program for performing one of the methods described herein.

A further embodiment in accordance with the invention includes an apparatus or a system configured to transmit a computer program for performing at least one of the methods described herein to a receiver. The transmission may be electronic or optical, for example. The receiver may be a computer, a mobile device, a memory device or a similar device, for example. The apparatus or the system may include a file server for transmitting the computer program to the receiver, for example.

In some embodiments, a programmable logic device (for example a field programmable gate array, FPGA) may be used to perform some or all of the functionalities of the methods described herein. In some embodiments, a field programmable gate array may cooperate with a microprocessor in order to perform one of the methods described herein. Generally, the methods are performed by any hardware apparatus. This can be a universally applicable hardware, such as a computer processor (CPU) or hardware specific for the method, such as ASIC.

The apparatuses described herein may be implemented, for example, by using a hardware apparatus or by using a computer or by using a combination of a hardware apparatus and a computer.

The apparatuses described herein or any components of the apparatuses described herein may be implemented at least partly in hardware and/or software (computer program).

The methods described herein may be implemented, for example, by using a hardware apparatus or by using a computer or by using a combination of a hardware apparatus and a computer.

The methods described herein or any components of the methods described herein may be performed at least partly by hardware and/or by software (computer program).

While this invention has been described in terms of several advantageous embodiments, there are alterations, permutations, and equivalents, which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention. 

1. Levelling system for a construction machine, in particular a road construction machine or a road finishing machine or a road milling machine, comprising: a layer thickness measurement system configured to measure a layer thickness currently to be applied or to be removed and respective actual layer thickness values for a plurality of positions or respective predicted actual layer thickness values for a plurality of positions, a processor configured to determine, based on a layer thickness profile comprising a plurality of set layer thickness values allocated to the plurality of the positions, as well as the actual layer thickness values or predicted actual layer thickness values for the positions, control values per position for height regulation of a tool of the construction machine.
 2. Leveling system according to claim 1, wherein the control values per position are selected such that the tool is raised and/or lowered according to the layer thickness profile, in order to be moved per position at a position according to the set layer thickness values; and/or wherein the control values per position are selected such that a determined deviation between an actual layer thickness value or predicted actual layer thickness value and a set layer thickness value is considered.
 3. Leveling system according to claim 1, wherein the processor is configured to determine the control value for the further position by considering the set layer thickness of the further position; and/or wherein the further position is offset by an offset with respect to the respective position.
 4. Leveling system according to claim 1, wherein the control values per position are selected such that in the settled state, the actual layer thickness value or the predicted actual layer thickness value per position essentially (±20%, ±10%, ±5%, ±3%, ±1 %) corresponds to the set layer thickness value per position; and/or wherein the control values are derived such that the height regulation of the tool is performed by considering the regulation path (offset) of the tool along a direction of travel of the construction machine.
 5. Leveling system according to claim 1, wherein the processor is configured to derive the control values from the layer thickness profile such that a layer to be smoothed or to be applied by the tool forms an even surface on an underground profile along a direction of travel of the construction machine; and/or wherein a layer to be applied or a layer to be smoothed comprises a first dimension along the direction of travel and a second dimension transversal to the direction of travel and wherein a plane is spanned by the first dimension and the second dimension and wherein the control values are derived from the layer thickness profile such that a layer to be applied (to be placed) or a layer to be smoothed by the tool comprises an even surface on an underground profile along the spanned plane.
 6. Leveling system according to claim 1 comprising a position sensor or GNSS sensor, in particular a position sensor or GNSS sensor coupled to the tool or coupled to the construction machine and wherein the position sensor or GNSS sensor is configured to determine the position for the actual layer thickness values or predicted actual layer thickness values, in particular the position along the direction of travel.
 7. Leveling system according to claim 1, wherein the layer thickness profile comprises varying set layer thickness values across the positions and/or along the direction of travel and/or wherein the layer thickness profile is determined in dependence on an underground profile.
 8. Leveling system according to claim 1, wherein the processor is configured to determine the control values such that a minimum layer thickness is provided per position.
 9. Leveling system according to claim 1, wherein the processor comprises an evenness regulator that is configured to determine the control values by using sensor values, such that an even surface is generated; and/or wherein the processor comprises a regulating path comprising a P component, an IT component, a PT component and/or a regulation path with a prediction model.
 10. Leveling system according to claim 1, wherein the layer thickness measurement system forms, together with the processor, a first control circuit for a first side (left or right) of the tool; and/or wherein the layer thickness measurement system or a further layer thickness measurement system forms, with the processor, a second control circuit for a second side of the tool; or wherein the layer thickness measurement system forms, together with the processor, a first control circuit for a first side (left or right) of the tool; and/or wherein the layer thickness measurement system or a further layer thickness measurement system forms, with the processor, a second control circuit for a second side of the tool, wherein the first and second control circuits interact in order to control the tool accordingly for the intermediate positions between the first and second side of the tool, such that the actual layer thickness essentially corresponds to the set layer thickness for intermediate positions in the settled state.
 11. Leveling system according to claim 1, wherein the layer thickness measurement system comprises at least one sensor in front of the screed and at least one sensor behind the screed and wherein the layer to be determined is determined by forming the difference.
 12. Leveling system according to claim 1, wherein the leveling system comprises a sensor arrangement comprising at least two, at least three or at least four sensors arranged at a carrier extending along the direction of travel of the construction machine; or wherein the leveling system comprises a sensor arrangement comprising at least two, at least three or at least four sensors that are arranged at a carrier extending along the direction of travel of the construction machine and wherein the sensor arrangement comprises the layer thickness measurement system.
 13. Construction machine, in particular road construction machine or road finishing machine or road milling machine comprising a leveling system according to claim
 1. 14. Apparatus for determining a layer thickness profile comprising a plurality of layer thickness values allocated to a plurality of positions, comprising: an interface for receiving an underground profile comprising a plurality of height values allocated to a plurality of the positions; an interface for receiving at least one set height or set depth; and a calculating unit for determining the layer thickness profile based on a difference between the plurality of height values allocated to a plurality of the positions and the at least one set height or set depth or a reference defined by the at least one set height or set depth.
 15. Apparatus according to claim 14 comprising an output interface for providing/exporting the layer thickness profile to a construction machine, in particular a road construction machine or a road finishing machine.
 16. Apparatus according to claim 14, wherein the at least one set height is defined by several set height values allocated to a plurality of the positions; wherein the at least one set depth is defined by several set depth values allocated to a plurality of the positions; or wherein the at least one set height and/or the several set height values define a plane or 3D plane of a layer to be smoothed or to be produced or generated (placed).
 17. Method for leveling for a construction machine, in particular a road construction machine or a road finishing machine or a road milling machine, comprising: measuring a current layer thickness to be applied or to be removed and determining respective actual layer thickness values or predicted actual layer thickness values for a plurality of positions, determining control values per position for height regulation of a tool of the construction machine based on a layer thickness profile comprising a plurality of set layer thickness values allocated to a plurality of the positions as well as the actual layer thickness values or predicted actual layer thickness values for the positions.
 18. Method for determining a layer thickness profile comprising a plurality of set layer thickness values allocated to a plurality of positions, comprising: receiving an underground profile comprising a plurality of height values allocated to a plurality of the positions; receiving at least one set height or set depth; and determining the layer thickness profile based on a difference between the plurality of height values allocated to a plurality of the positions and the at least one set height or set depth or a reference defined by the at least one set height or set depth.
 19. A non-transitory digital storage medium having a computer program stored thereon to perform the method for leveling for a construction machine, in particular a road construction machine or a road finishing machine or a road milling machine, the method comprising: measuring a current layer thickness to be applied or to be removed and determining respective actual layer thickness values or predicted actual layer thickness values for a plurality of positions, determining control values per position for height regulation of a tool of the construction machine based on a layer thickness profile comprising a plurality of set layer thickness values allocated to a plurality of the positions as well as the actual layer thickness values or predicted actual layer thickness values for the positions, when said computer program is run by a computer.
 20. A non-transitory digital storage medium having a computer program stored thereon to perform the method for determining a layer thickness profile comprising a plurality of set layer thickness values allocated to a plurality of positions, the method comprising: receiving an underground profile comprising a plurality of height values allocated to a plurality of the positions; receiving at least one set height or set depth; and determining the layer thickness profile based on a difference between the plurality of height values allocated to a plurality of the positions and the at least one set height or set depth or a reference defined by the at least one set height or set depth, when said computer program is run by a computer. 